Using Control Charts for Temperatures In Exercises 2–4 in Section 13-2, the amounts of electrical energy consumption were listed for the author’s home during a period of four recent years. The accompanying table lists the average temperature (in degrees Fahrenheit) for the same time periods. Use appropriate control or run charts to determine whether the data appear to be part of a statistically stable process.

Jan.–Feb. Mar.–Apr. May–June July–Aug. Sept.–Oct. Nov.–Dec.

Year 1 32 35 59 76 66 42 Year 2 22 33 56 70 63 42 Year 3 30 38 55 71 61 38 Year 4 32 40 57 72 65 45